One of my cats (Kiri) recently had surgery to correct some pretty serious tooth decay issues, and ever since then my other cat (Killer) has been very aggressive, which I think may be due to non-recognition. Before the surgery Kiri had some pretty bad breath, and I'm thinking it's possible that Killer doesn't recognize her because the smell is no longer there?

At first Killer was full-on attacking Kiri; yowling, hissing, biting, scratching; and even though I always broke it up quite quickly, Kiri started feeling the need to fight back, to the point of growling/hissing even before Killer started. I bought a new litter box because Kiri would hide in the living room and use the corner because she was afraid to walk across the apartment. I started keeping them separated more and more, until eventually I kept Killer in my bedroom alone for a full week to see if she'd forget about the whole thing.

Kiri quickly became more confident with Killer locked up, but Killer would still hiss at the door if she knew Kiri was on the other side. Near the end of the week she seemed to be calming down so we slowly reintroduced them to each other and other than a couple of hisses they've been somewhat civil but not friendly.

However, soon after the reintroduction, Killer started vomiting up her food and kept doing it about once every couple of hours until it was just foam. It's become much less frequent, but I also don't think she's eating anywhere near as much as usual. She seems much less aggressive and more fearful, and now Kiri seems to be the one to hiss first when Killer is minding her own business.

I'm not really sure what to do; it seems pretty clear to me that the vomiting and lack of appetite on Killer's part is due to stress, and I don't want to stress her out more by taking her to a vet if there's nothing a vet could do. Ive tried those herbal calming drops and they didn't do anything. Should I keep them separated again? Do those calming collar work at all? What can I try feeding her that will settle her stomach?

Thanks so much in advance for your help and concern.

***EDIT***
I grew concerned after Killer refused to eat some of her favorite foods (raw chicken, nupro cat supplements, parmesan cheese, even junky cat treats!) so I tried syringe feeding her some water and mushed up kibble and she immediately vomited it back up. The vomit had a definite green tinge to it too. Definitely taking her to the vet tomorrow, if only to check on her hydration, but does this sound like anything in particular to anyone? An intestinal blockage maybe?

I think a vet visit is definitely in order. Whatever it is it doesn't sound good.

When both cats are back in the house you might keep them separated for a bit and exchange smells with a towel or a blanket. You can also try gently wiping them both with baby powder and/or putting a dab of vanilla under both their chins and at the base of the tails so they smell the same.

Took her into the vet, he didn't find anything obviously wrong with her other than a minor wheeze on one side (not serious enough to be asthma) and slight constipation. She wasn't even dehydrated, which means she must have been drinking water without me knowing? He gave me the choice of antibiotics in case that happened to solve the problem or bloodwork and I chose bloodwork, so hopefully I get some answers tomorrow.

Took her into the vet, he didn't find anything obviously wrong with her other than a minor wheeze on one side (not serious enough to be asthma) and slight constipation. She wasn't even dehydrated, which means she must have been drinking water without me knowing? He gave me the choice of antibiotics in case that happened to solve the problem or bloodwork and I chose bloodwork, so hopefully I get some answers tomorrow.

I would had pick the blood too, I do not like to give my dog antibiotics unless
he needs them. Does the vet have any idea why your cats are not getting along after the surgery?

I mentioned non-recognition aggression to him and he said he'd never heard of it before but it sort of made sense because Kiri's smell is so different. The bloodwork came back today and everything was just fine except for some dehydration. He's recommending the antibiotics again to see if that does anything so I'll pick those up tomorrow morning.

When I came home from work today I gave Killer some wet food and even though she ate it, she ended up vomiting it up a couple minutes later. Does this sound like it could be a blockage or something?

Quote:

Originally Posted by Barkingdog

I would had pick the blood too, I do not like to give my dog antibiotics unless
he needs them. Does the vet have any idea why your cats are not getting along after the surgery?

I mentioned non-recognition aggression to him and he said he'd never heard of it before but it sort of made sense because Kiri's smell is so different. The bloodwork came back today and everything was just fine except for some dehydration. He's recommending the antibiotics again to see if that does anything so I'll pick those up tomorrow morning.

When I came home from work today I gave Killer some wet food and even though she ate it, she ended up vomiting it up a couple minutes later. Does this sound like it could be a blockage or something?

I would keep an eye on this , if your cat vomit up her food again I would have the vet check her out, it could be a blockage . What are the side effect of the antibiotics , does it cause cats to vomit? Or maybe she has a fur ball that causing her to vomit.

Hi
I'm no expert, but experience over the past number of years with my own medically compromised cat, has taught me a few things. A lot of my knowledge has come from a myriad of sources.
Your teminology - "non recognition aggression" - fits the bill to a tee. What happens is this. Killer has sensed a change that Kiri went through and the scents that she gave off on entrance to the house when coming back from the dental surgery are different. To Killer, this would be a sign of a new animal into her territory. Kiri would be giving off the scent of being a wounded animal as a result of the surgery, plus the smells from the other animals at the vet's office, plus the smells from the vet office itself. For some unknown reason, cats don't recognize one another visually when put under undue stress, they rely more on scent and what their nose tells them rather than what they see.
Cats are not the same as "pack animals" when put under extreme stress. Dogs and pack animals have three methods of dealing with a threatening confrontation - fight, flight, and submission. With cats it is only the 2 - fight and flight. By the sound of it, the change was so dramatic that it put Killer into the fight mode because there was no place to run, and her territory was being intruded by a strange cat.
Having said that, it could be very difficult to get things back on an even keel. You mentioned that you tried "herbal calming drops" What were they? I've used calming remedies with some success depending on what and how they are administered. You've already done the "separation" bit, and you may have to do it again over a longer period, due to the fact that Killer perhaps doesn't recognize Kiri and feels that there is a "new" cat in the house. If you decide to go this route, please let me know. I can give you some ideas on how to set up a safe room so they can see one another but not interfere with one another.
Something that you might want to try is a Thundershirt. There is some talk of them in the last day or so in one of the blogs regarding them and dogs. They make them for cats as well. I'll include the web site for you to look at. There was some mention of Pet Valu carrying them, but I don't know if they carry them for cats.
Possibly a calming agent from the vet might help both of them. I think I would be using aloe vera juice on Killer to help cool and heal her stomach after all the vomiting. If you go that way, make sure that you get a certified organic preservative free aloe vera juice, Lily of the desert is one thatfits that description.

As far as giving antibiotics to Killer, I'd be very leery of doing that because my epxerience has been that it upsets their stomachs and Killer already has a stomach issue if she is vomiting. Antibiotics also tend to kill off good bacteria as well as the bad.in the digestive system.

Also, the re-action that Killer is exuding could suggest a possible previous bad experience with something. You do not mention at what age you obtained the two kitties, nor under what circumstances you got them. It could have been something associated with a vet office or another environment and it could have triggered a re-call of something very traumatic.

Hopefully some of this information is helpful to you and will trigger responses from other people in the know.

Up until today things seemed to be looking up, the cats have been fighting way less, and when they do fight it's been milder hissy fits and not trying to kill each other. Kiri has been keeping to herself in one area of my living room but she has seemed happy enough and Killer has been leaving her alone for the most part. Killer stopped vomiting and acting sick after only a day or two of antibiotics and tbh I don't think the antibiotics really did anything.

However, this evening Kiri inexplicably urinated on my couch, right beside me, as if she wanted me to notice it. I know that this can happen if a cat is stressed or it's too afraid to go to the litter box, but the box is literally right beside the couch, and she didn't seem overly stressed at the time. Almost immediately afterwards, the cats got in their worst fight in a long while.

I honestly don't expect anyone to have any clear answers on what to do since I believe I've done close to everything already, but at this point I'm just hoping for reassurance that all this drama will someday end. After almost two and a half months and hundreds of dollars, I'm wondering if it might soon be time to look for a new home for one of them. I don't want them to be in a state of constant fear in their own home, but I don't know what else I can do. Keeping them separated in my one bedroom apartment just can't be the long-term solution.